Size of "drawing grid" does not reset to match font size when font size changes

[TheGreenHerring]

When any of the picture size guides from the View ➡ Guides menu are enabled (e.g. Smallscale (80×25)), they will automatically reset to the correct size in relation to the font size whenever the font size changes in any way, such as from loading any font (bundled or from disk), or from enabling the Use 9px Font toggle. However, the same does not apply to the grids from the Drawing grids submenu of View ➡ Guides: if the font size changes while any of the grids are enabled, the grid blocks will remain the size of the previous font rather than resizing to fit the new one. The only remedy is to switch to a different grid, or to turn off the grid and then turn it back on.

(NOTE: This bug also exists in regular Moebius and was not introduced by forks.)